Android 4.3 upgrade corrupted old files?

My Nexus 7 tablet was automatically upgraded to Android 4.3. This o/s platform contains, among other features, better disk management code called TRIM, which helps prevent storage fragmentation. After the Android s/w update (and subsequent platform reboot), I noticed some of my old encrypted data had been partly corrupted, and in one case, totally corrupted when the app's decryption step completed. The app did not report a decryption error, but the output was incorrectly decoded, especially at the beginning of the text block. Major mystery!!!